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read command - using output from command substitution
Post 302453288 by ProGrammar on Tuesday 14th of September 2010 05:32:40 PM
09-14-2010
read command - using output from command substitution
Hey, guys!
Trying to research this is such a pain since the read command itself is a common word. Try searching "unix OR linux read command examples" or using the command substitution keyword.
So, I wanted to use a command statement similar to the following.
This is kinda taken from another question I posted recently about string manipulation and extracting portions of a string (in order to store to variable, via command substitution).
$ TEMPFILE=`ls -1 *31AUG2010.txt`
yields $TEMPFILE=filetransfers_31AUG2010.txt
$ read DD MM YY<enter>
> `echo ${TEMPFILE:14:2}` `echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`<enter>
which yields:
$DD=`echo
$MM=${TEMPFILE:14:2}`
$YY=`echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`
As you can see, I had intended for each variable to store the output from each command substitution set, but instead stored the literal values between each space encountered on the following input lines. BOOOOO!!
I don't even know if what I'm attempting to do is possible, I wanted to do this in a for loop, storing a new corresponding value for each variable per command set iteration.
Anybody have any experience with this, or how to get command substitution output to work with the read command?
I know that I could just do the command substitution independently for each variable in the loop, but now I'm just curious to know if it's possible to accomplish in one line using the read command.
This is just for my curiosity, but I'd appreciate if somebody could educate me on this matter.
Trying to research this is such a pain since the read command itself is a common word. Try searching "unix OR linux read command examples" or using the command substitution keyword.
So, I wanted to use a command statement similar to the following.
This is kinda taken from another question I posted recently about string manipulation and extracting portions of a string (in order to store to variable, via command substitution).
$ TEMPFILE=`ls -1 *31AUG2010.txt`
yields $TEMPFILE=filetransfers_31AUG2010.txt
$ read DD MM YY<enter>
> `echo ${TEMPFILE:14:2}` `echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`<enter>
which yields:
$DD=`echo
$MM=${TEMPFILE:14:2}`
$YY=`echo ${TEMPFILE:16:3}` `echo ${TEMPFILE:19:4}`
As you can see, I had intended for each variable to store the output from each command substitution set, but instead stored the literal values between each space encountered on the following input lines. BOOOOO!!
I don't even know if what I'm attempting to do is possible, I wanted to do this in a for loop, storing a new corresponding value for each variable per command set iteration.
Anybody have any experience with this, or how to get command substitution output to work with the read command?
I know that I could just do the command substitution independently for each variable in the loop, but now I'm just curious to know if it's possible to accomplish in one line using the read command.
This is just for my curiosity, but I'd appreciate if somebody could educate me on this matter.
Last edited by ProGrammar; 09-14-2010 at 06:34 PM.. Reason: elaboration, clarification
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apply
apply(1) General Commands Manual apply(1) NAME
apply - Applies a command to a set of arguments SYNOPSIS
apply [-acharacter] [-number] command argument... The apply command runs the specified command on each argument in turn. OPTIONS
Identifies the character used instead of the % (percent sign) to designate argument substitution strings. Specifies the number of argu- ments to be passed to command. DESCRIPTION
Normally, arguments are chosen individually; the optional number specifies the number of arguments to be passed to command. If number is 0 (zero), command is run without arguments once for each argument. If you include character sequences of the form %n (where n is a digit from 1 to 9) in command, they are replaced by the nth unused argument following command when command is executed. If any such sequences occur, number is ignored, and the number of arguments passed to command is the maximum value of n in command. You can specify a character other than % (percent sign) to designate argument substitution character strings with the -a option; for exam- ple, -a@ would indicate that the sequences @1 and @2 were to be replaced by the first and second unused arguments following command. NOTES
Shell metacharacters in command may have undesirable effects; it is best to enclose complicated commands in ' ' (single quotes). There is no way to pass a % (percent sign) followed immediately by any number if % is the argument expansion character. EXAMPLES
The following command is similar to ls: apply echo * The following command compares the file a1 to the file b1, a2 to b2, and so on: apply -2 cmp a1 b1 a2 b2 ... The following command runs who 5 times: apply -0 who 1 2 3 4 5 The following command links all files in the current directory to the directory /usr/joe: apply 'ln %1 /usr/joe' * SEE ALSO
Commands: sh(1), xargs(1) apply(1)